1. Field of the Invention
The present general inventive concept relates to an apparatus and a method of processing a voice signal of a mobile terminal in a mobile communication system, and more particularly, to an apparatus and a method of processing a received-voice signal of a mobile terminal in a mobile communication system.
2. Description of the Related Art
Generally, a mobile terminal is a device with which a user can transmit and receive voice and data in a mobile environment anywhere at any time. There are various kinds of mobile terminals, such as a cellular phone, a WAP (Work Analysis Program) phone, a PDA (Personal Digital Assistants), and a Web Pad, and such mobile terminals are used by many people for personal service and extension of mobility.
In a voice call using a mobile terminal, the call is generally performed under a condition where ambient noise exists. An influence of the noise may be considered from a standpoint of transmission and reception.
First, from the standpoint of transmission, in a case in which a signal is input into a microphone, ambient noise as well as a voice of a transmitter is input. Accordingly, when this ambient noise and voice is encoded as is and transmitted, it is difficult for a receiver to recognize a received voice due to a low SNR (Signal-to-Noise Ratio). Taking this characteristic into account, noise removal on a signal input by a microphone is performed by using hardware (H/W) or software (S/W) in voice transmission. The above described method of removing the ambient noise of the transmitter is generally widely used at present.
Meanwhile, from the standpoint of reception, when noise is present and strongly occurs around the receiver, the received voice cannot be clearly recognized. Moreover, the transmitter cannot recognize the state of the noise occurring around the receiver, and thus a countermeasure against the noise occurring around the receiver has to be considered based on the receiver-side of a transmitted input signal.
Hereinafter, methods of eliminating the influence of the noise occurring around the receiver, on the receiver-side of the transmitted input signal, will be described.
In a first method, during the occurrence of noise, a volume key is used to increase a reception volume. In this method, whenever a level or state of the noise is changed, it is required to vary volume settings. Taking this characteristic into account, the method employs an automatic change of a volume according to a noise level. However, in this case, since both noise and voice are included in microphone input, it is necessary to additionally mount a noise measuring microphone at a position as far as possible from a call microphone in which noise is input in order to separate the voice from the noise.
In a second method of reducing the influence of the noise occurring around the receiver, it is determined if an input signal includes voice, and a calculated gain is applied only when the input signal includes noise. However, in this case, the determination of whether each input includes voice, increases computational complexity, and also, the computational complexity increases in proportion to an overall precision of this method.
In a third method, gain values are stored in a gain table. During a voice duration, a previous gain value is maintained. In a noise duration, a changed gain value is applied. However, the voice duration is required to be calculated each time an input signal includes voice, thus, the computational complexity increases.
As described above, the prior art has performed operations for compensating received voice based on calculations of the level of ambient noise at the receiver-side of a transmitted input signal. However, an operation of determining when the input signal is voice or noise through an analysis of the characteristic of the input signal is required each time, and thus, power consumption and time delay occur.